SWODY2
SPC AC 170600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT SAT SEP 17 2011
VALID 181200Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A PROGRESSIVE/RELATIVELY LOW AMPLITUDE UPPER FLOW REGIME WILL
CONTINUE THROUGH SUNDAY...WITH THE MAIN BELT OF WESTERLIES CONFINED
TO THE NORTHERN THIRD OF THE CONUS. THIS PATTERN WILL BE HIGHLIGHTED
BY AN EASTWARD-MOVING SHORTWAVE TROUGH AND A DEGREE OF AMPLIFICATION
OVER THE NORTHERN PLAINS/UPPER MIDWEST AND
SASKATCHEWAN/MANITOBA/NORTHERN ONTARIO.
...MUCH OF THE SOUTHERN PLAINS/OZARKS TO MIDDLE MS VALLEY...
A RELATIVELY MOIST AIRMASS /MAINLY LOWER 60S F SURFACE DEWPOINTS/
WILL REMAIN INTO SUNDAY ACROSS THE SOUTHERN PLAINS TO THE EAST OF A
SURFACE TROUGH/DRYLINE...WHILE MOISTURE OTHERWISE SPREADS
NORTHEASTWARD ACROSS THE OZARKS/MIDDLE MS VALLEY AHEAD OF AN
EAST-SOUTHEASTWARD MOVING COLD FRONT /WITH THIS FRONT GRADUALLY
OVERTAKING THE PRE-FRONTAL TROUGH ACROSS OK AND NORTHWEST TX/. WHILE
EARLY DAY PRECIPITATION PROVIDES A DEGREE OF UNCERTAINTY...AMPLE
PRE-COLD FRONTAL HEATING SHOULD CONTRIBUTE TO POCKETS OF MODERATE
SURFACE-BASED DESTABILIZATION DURING THE AFTERNOON ESPECIALLY ACROSS
PORTIONS OF OK/TX INTO SOUTHERN/EASTERN KS. SURFACE BASED
DESTABILIZATION IS MORE UNCERTAIN /BUT LIKELY MUCH WEAKER/ ACROSS
THE OZARKS/MIDDLE MS VALLEY AS CLOUD COVER/PRECIPITATION MAY BE
PERSISTENT.
WHILE AMPLE POTENTIAL INSTABILITY AND THE INFLUENCE OF MODEST
CYCLONIC FLOW ALOFT MAY CONTRIBUTE TO SOME SEVERE POTENTIAL IN THE
FORM OF WIND AND HAIL MAINLY SUNDAY AFTERNOON/EVENING...VERTICAL
SHEAR /GENERALLY 25-30 KT/ IS EXPECTED TO BE RELATIVELY WEAK GIVEN
THAT THE PRIMARY WESTERLIES/PROGRESSIVE SHORTWAVE PERTURBATION WILL
BE OVER THE NORTH-CENTRAL CONUS. GIVEN MODEST SHEAR...WEAKENING MASS
CONVERGENCE WITH TIME...AND UNCERTAINTY REGARDING EARLY DAY
PRECIPITATION/EXACT DEGREE OF DESTABILIZATION...WILL DEFER TO
SUBSEQUENT OUTLOOKS FOR REEVALUATION OF A POSSIBLE SLIGHT RISK FOR
AREAS SUCH AS OK/NORTHWEST TX.
..GUYER.. 09/17/2011
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